Renal medullary interstitial cells have been isolated from rabbits and grown in tissue culture. These cells exhibit characteristic lipid containing vacuoles on light and electron microscopic examination. These cells in tissue culture produce large quantitites of prostaglandins E and F, as measured by radioimmunoassay. Prostaglandin E production is stimulated by arachidonic acid, bradykinin, angiotensin II, anti-diuretic hormone, and hyperosmolarity. Prostaglandin production is decreased by potassium, acetyl salycylic acid, indomethacin, ibuprofen and meclofenamic acid.